1) Field of the Invention
The present invention relates to testing of electrical machines in general and more particularly to methodology to select the optimum levels of test to use in testing said electrical machines.
2) Prior Art
The testing of manufactured devices to ensure that they meet a desired standard is an integral part of most, if not all, manufacturing processes. The conventional manufacturing process revolves relative to an assembly line along which components or parts are provided and assembled by robots or humans into a specific device such as a computer, printer, etc. The assembled devices are then tested and shipped if the tests show the devices meet a desired specification or reworked if the tests show otherwise.
One of the goals of the manufacturing process is to minimize manufacturing costs so as to keep the device cost competitive and possibly below the cost of products from competing manufacturers. It is often said the low cost manufacturer will capture market share from other manufacturers. As a consequence the competition is fierce to keep manufacturing cost at the lowest possible level.
One of the components of manufacturing costs is the cost associated with testing. It is recognized that the fewer number of test executed on a machine the less time the machine has to be retained on the manufacturing line and the lower will be the test cost for testing. Conversely, the higher the number of tests executed on the machine the longer it has to be retained on the manufacturing line and the manufacturing cost will be higher.
Because testing is used to eliminate poor quality or defective devices from the product stream, it is recognized testing has to be done at a sufficiently high level to root out defective devices. Failure to eliminate defective devices from the product line may result in increased warranty cost and/or customer dissatisfaction. As discussed above testing impacts manufacturing test time which impacts manufacturing costs. Stated another way, the test level selected influences manufacturing test time, product quality and customer satisfaction.
Several test level solutions are provided in the prior art. All are fixed and not adjustable. In one test level solution termed “full test” the test/tests applied is/are such that the maximum test time allotted is exhausted. This is not a desirable solution because it results in lower manufacturing capacity and increases the need for additional space and facilities. In addition, the facilities are also underutilized during non-manufacturing peak period (details discussed hereinafter). The solution is also costly since the test time is always maximum.
In another solution termed “minimal test” the test/tests applied is/are such that the minimum test time allotted is exhausted. Even though this solution results in quicker testing, it could also result in poor quality product which could lead to customer dissatisfaction and higher warranty repair costs. The facilities are also underutilized during non-peak manufacturing periods since additional tests are not done.
In still another solution termed “partial test” sufficient tests are run for a period of time less than maximum allotted time and more than the minimum allotted time. This solution generally provides a better cost/benefit than either of the above solutions, but it ends up under-testing the parts that may have poorer quality levels, and over-tests parts that may not need as much testing. In addition, if partial testing levels are set based on historical quality performance, there is an exposure that a commodity that has had a premium performance history could be affected by a new quality problem that would be undetected because only a reduced test is being performed. The facilities are also being underutilized during non-peak periods since additional testing could be taking place for failure screening and data collection purposes.
In view of the above there is a need to provide a more efficient test solution for testing devices, such as computers, that minimizes the time and expenses presently required and at the same time not compromising product quality.